In the early stages of the pandemic H1N1 influenza outbreak in Chicago, blacks and Latinos were about four times more likely than Caucasians to contract the virus, according to the first study that has examined the racial composition of those who caught the flu. Children were also 14 times as likely as the elderly to contract the virus, according to a report from the Chicago Department of Public Health in today's edition of the Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report.
Despite the figures, CDC officials said it is unlikely that there is any genetic factor underlying the increased susceptibility. Rather, both blacks and Latinos suffer from higher rates of asthma, diabetes and other medical conditions that make them more susceptible to the new virus, commonly known as swine flu.
Illinois and Wisconsin had an unusually high incidence of laboratory-confirmed cases of the flu, surprising because of their distance from Mexico, the initial focus of the outbreak. But both states had aggressive laboratory testing programs and most likely simply detected a higher number of cases that would otherwise have gone unnoticed.
Today's report showed 1,557 laboratory-confirmed cases of pandemic H1N1 virus in Chicago in the 14 weeks ending July 25. Children ages 5 to 14 had the highest infection rate, 147 cases per 100,000 population -- 14 times higher than that for adults over the age of 60. Previous studies have shown that the elderly, who are normally the primary victims of seasonal flu, may have some resistance to the new virus because of previous exposures to swine-related flu viruses. A total of 205 patients were hospitalized, about 13% of those infected. Children up to 4 years old had the highest hospitalization rate, 25 per 100,000, followed by those aged 5 to 14 at 11 per 100,000.
Blacks were hospitalized at a rate of nine per 100,000 and Latinos at eight per 100,000, compared to the rate of two per 100,000 in Caucasians. Earlier this month, Boston public health authorities released some preliminary information suggesting that blacks and Latinos accounted for three-quarters of hospitalizations in that city. But Dr. Dan Jernigan of the CDC noted that the early stages of the epidemic struck neighborhoods rather randomly, and the outcomes might be due simply to chance -- as well as the higher rate of underlying disease in those populations.
Among the 205 hospitalized patients, 40 were admitted to the intensive care unit and nine required mechanical ventilation. Fourteen of the hospitalized patients were pregnant, one of whom died after giving birth by caesarean section. Among the 177 hospitalized patients for whom information was available, 37 (21%) had a previous diagnosis of asthma and 13 (7%) had a diagnosis of diabetes.
-- Thomas H. Maugh II